The Third Generation Project Partnership (3GPP) has developed the System Architecture Evolution (SAE) as the core network architecture of its future and Long Term Evolution (LTE) wireless mobile telecommunications standard. The main component of the SAE architecture is the Evolved Packet Core (EPC). The LTE/SAE network includes network entities supporting the user and control planes.
An ongoing trend within telecommunications is the convergence of fixed and mobile networks, which is known as Fixed Mobile Convergence (FMC). The trend of evolving networks towards the use of IP-based technologies is common to both fixed and mobile networks, which makes the convergence easier. Through FMC, mobile and fixed network operators will be able to utilize their network resource more efficiently, which leads to reduction of capital and operational expenditure. For instance, when a user is running an IP-based application such as Multimedia Telephony (MMTel) inside their home, it is more efficient to utilize broadband connectivity of the fixed access network rather than the wireless access network.
Residential networks have been important to the success of FMC because they are the most commonly used fixed network access by ordinary users. Therefore, it is important to be able to connect mobile phones to the Evolved Packet Core (EPC) through a residential network. Note that the term User Equipment (UE) is used interchangeably herein in place of the term mobile phone or mobile terminal. The term UE is used throughout the 3rd Generation Partnership Project (3GPP) documentation, and is intended to refer to any piece of equipment that is configured to access the internet; it would include, for example and without limitation, mobile telecommunication devices, portable or handheld computing devices and desktop or installed computers. However, for the purposes of this disclosure and the inventive techniques described herein, the term is not necessarily limited to devices that support 3GPP standards.
3GPP defines mobile 2G/3G/LTE accesses and “non-3GPP accesses.” See 3GPP TS 23.402, “3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Architecture enhancements for non-3GPP accesses”. The latter, non-3GPP accesses can include access through a fixed network. The BroadBand Forum (BBF) is a standardization organization developing standards for fixed access (see http://www.broadband-forum.org/) and defines an architecture for fixed networks. There is an ongoing joint work item on FMC between these two organizations [3GPP TR 23.839, now moving into TS 23.139, and BBF WT 203].
Many UEs address the FMC trend by providing multiple radio interfaces: one interface to connect to a 2G/3G/LTE access and a WiFi interface to connect to a fixed network.
3GPP TS 23.402 defines different ways for a UE to connect to the 3GPP core network (EPC) via a non-3GPP access network. In particular, there are several ways defined to attach a 3GPP UE via a BBF domain. 3GPP defines four access procedures: (trusted) S2a, (untrusted) S2b, trusted S2c, untrusted S2c; these can more generally be considered as three access procedures S2a, S2b and S2c.
These are shown in FIG. 1 of the accompanying drawings, which illustrates the key entities and network paths involved between a UE 10b and a mobile access network with EPC components 31. As illustrated in FIG. 1, UE 10b connects to a Broadband network, in this example a Broadband Home Network 12b, and then via a BBF-defined access network 20 to the Evolved Packet System 30. Also shown are other equipment entities that connect to the Broadband Home Network 12b, such as a WiFi Access Point (AP) 13b, a TV 14b with set-top box 15, a personal computer 16, a Media centre 17 and a printer 18. The WiFi access domain could be, e.g., a residential network or an operator provided hotspot.
A Residential Gateway (RG) 19 in the Broadband Home Network 12b connects to an access node (AN) 21 in the BBF-defined access network 20, which in turn connects to a Border Network Gateway (BNG) 22. In certain configurations, the Residential Gateway (RG) 19 and WiFi Access Point (AP) 13b might be co-located in the same physical device. Other entities in the BBF-defined access network 20 that connect to the BNG 22 include a Broadband, or BBF, Policy Control Function (BPCF) 23, a BBF Authorisation and Accounting server (BBF AAA) 24 and other fixed operator services 25.
In the Evolved Packet System 30 is a PDN Gateway (PDN-GW) 32, to which user data packets are sent by one of the three methods S2a, S2b, S2c. In addition, the Evolved Packet System 30 includes the mobile access network with EPC components 31, accessed via a Serving Gateway 33, a Policy and Charging Rules Function (PCRF) 34, a 3GPP Authorisation and Accounting server (3GPP AAA) 35, a user's Home Subscriber Server (HSS) 36, a Security Gateway (SeGW) 37 and other entities 38 for the Operator-provided IP services. For some accesses an Evolved Packet Data Gateway (ePDG) may be provided between the PDN-GW 32 and the external gateway node (in this case the BNG 22).
A 3GPP UE can attach to a BBF access network and connect to one or more PDNs via the S2 interface [3GPP TS 23.402]. Each PDN connection is anchored in a 3GPP PGW. The UE receives one IP address for each PDN connection. It is the PDN-GW (PGW) that assigns the address.
Of the three basic types of S2 interface, S2b and S2c overlay the BBF network and do not impact BBF. S2a is a more converged solution that does impact BBF nodes.
In S2a, there is a GPRS Tunneling Protocol (GTP) or Proxy Mobile IP (PMIP) tunnel for each PDN connection between the BBF BNG and the 3GPP PGW(s). Between the UE and the BNG a point-to-point link is required in order to separate the traffic from the different PDN connections. Such a point-to-point link can be implemented in several ways. One strategy to implement this point-to-point link is illustrated in FIG. 2A of the accompanying drawings. A UE 2 connects to a 3GPP domain 4 via a BBF Domain 6. The BBF Domain 6 comprises a Residential Gateway (RG) 8, an Access Node (AN) 10 and a BNG 12. The 3GPP domain 4 comprises one or more PDN Gateways (PGWs) 14.
An assumption can be made that the network between the UE and BNG is Ethernet-based. All nodes between the UE and the BNG do forced-forwarding towards the BNG on Layer 2 (L2; Ethernet). The BNG always sends downstream traffic targeted for the UE as unicast on L2, even if that traffic is multicast/broadcast on Layer 3 (L3; IP).
Such an implementation imposes a limited impact on the UE and the existing BBF infrastructure. More importantly, there is no impact to the UE if the UE only has one default PDN connection. The BNG can distinguish the different PDN connections based on the UE MAC address combined with the PDN connection IP address that was assigned to the UE.
It is to be noted that there are other ways to implement a point-to-point link between the UE and the BNG. Examples are: a L3 tunnel (e.g. IPsec or IP-in-IP), a L2 tunnel (e.g. L2TP), etc. However, all of these have a bigger impact on the UE or the BBF infrastructure.
Additional standardization activities are ongoing in the WiFi Alliance. In the WiFi Alliance, one of the focus areas is (public) hotspots. Therefore, in addition to the residential networks described above, hotspots are increasingly becoming key to the success of FMC, and there is a work item in 3GPP called SaMOG (Study on S2a mobility based on GTP & WLAN access to EPC; see 3GPP TR 23.852 at http://www.3gpp.org/ftp/Specs/html-info/23852.htm).
SaMOG is specific to S2a, but not specific to BBF. In S2a, the non-3GPP access network is seen as trusted; the non-3GPP access network is therefore denoted as TNAN (Trusted Non-3GPP Access Network). Where the TNAN uses Wireless LAN (WLAN) as the radio technology towards the UEs, the TNAN is denoted as TWAN (Trusted WLAN Access Network).
S2a over TWAN is now standardized in 3GPP [Chapter 16 of 3GPP TS 23.402]. FIG. 2B of the accompanying drawings is a schematic block diagram providing an architecture overview, illustrating a UE 2 connecting to a 3GPP domain 4 via a TWAN 6. The TWAN 6 comprises a Residential Gateway (RG) 8, an Access Node (AN) 10 and a gateway node denoted as a TWAN Access Gateway (TWAG) 12. The 3GPP domain 4 comprises one or more PDN Gateways (PGWs) 14. Also shown in FIG. 2B is a Trusted WLAN Access Point (TWAP), of which the BBF AAA 24 of FIG. 1 is an example; this will be described in more detail below.
In S2a, there is a GPRS Tunnelling Protocol (GTP) or Proxy Mobile IP (PMIP) tunnel for each PDN connection between the TWAG 12 (e.g. a BBF Border Network Gateway (BNG)) in the TWAN 6 and the 3GPP PGW(s). Each PDN connection is anchored in a 3GPP PGW. The UE receives one IP address for each PDN connection, and it is the PGW that assigns the address. Similarly, between the UE 2 and the TWAG 12 a point-to-point link is provided in order to separate the traffic from the different UEs and PDN connections.
A point-to-point link can be considered to be a protocol that provides a logical direct connection between two networking nodes. A data frame sent from node A via a point-to-point link to node B will not pass a node C. Note that a “point-to-point link” is a logical concept and can be implemented in several ways. The network between the UE 2 and the TWAG 12 would generally be Ethernet based, and examples of a point-to-point link between the UE 2 and TWAG 12 are: a L3 tunnel (e.g. IPsec or IP-in-IP), and a L2 tunnel (e.g. L2TP); however the technique disclosed herein is applicable to any data link layer or delivery protocol as will become apparent.
The correspondence between FIG. 2A and FIG. 2B will be clear. Note that the TWAG may also be standalone, such that there could be one BNG node and another TWAG node. The TWAG would then be above the BNG. The TWAG terminates the S2a interface.